A new molecular multiplex IgE assay for the diagnosis of pollen allergy in Mediterranean countries: A validation study

Abstract

Background: The identification of the primary sensitizing pollen is difficult in Southern European patients with Seasonal Allergic Rhinitis (SAR) if sensitized to various pollen sources with overlapping seasonality. A more precise diagnosis is obtained by IgE assays to allergen molecules, currently available as singleplex or microarrays.

Objectives: To test the analytical performance of a multi-parameter immunoblot molecular "Pollen Test" specifically designed to test IgE antibodies to pollen extracts and molecules clinically relevant in Southern Europe.

Methods: Sera were obtained from 101 children and 98 adults with SAR and tested with a customized multiplex immunoblot assay (EUROLINE Southern European Pollen Profile [ESEP]; EUROIMMUN AG, Luebeck, Germany) containing a comprehensive panel of allergen extracts and molecules. ESEP's outcomes were then compared in selected sera (ESEP positive to negative = 2:1) with those of singleplex IgE assays (ImmunoCAP; ThermoFisher Scientific, Uppsala, Sweden). For each of the examined reagents, qualitative (sensitivity, specificity, accuracy), semi-quantitative (classes) and quantitative (Spearman's rank correlation, Bland-Altmann plots) comparisons were performed.

Results: Compared to ImmunoCAP, cumulative ESEP's sensitivity and specificity were 87% (95% CI 84%-90%) and 88% (83%-93%) for extracts and 99% (98%-100%) and 87% (83%-91%) for molecules. Cohen's kappa coefficients (κ_C ) ranged for extracts from 0.18 (Pellitory) to 0.50 (Cypress) and for molecules from 0.21 (Ole e 1) to 0.68 (Phl p 7). The quantitative outcomes of the two diagnostic tests were highly correlated, with Spearman's rank correlation coefficients always exceeding 0.80. Bland-Altmann plots showed a tendency of ESEP to overestimate serum specific IgE levels, when compared to ImmunoCAP.

Conclusions and clinical relevance: Sensitivity and specificity of ESEP in testing serum IgE antibodies against pollen allergen extracts and molecules, in Italian patients with SAR, both exceeded 85%. The advantages and limitations of a multiplex customized immunoblot assay, in the routine clinical use of molecular diagnostics in Southern European pollen allergic patients, deserve to be tested.

Keywords: allergen-specific immunotherapy; component-resolved diagnostics; immunoglobulin E; pollen; precision medicine; seasonal allergic rhinitis.